CGTalk - Arm IK Freaking Out

GreenShellFactor

04-09-2007, 03:07 AM

Okay, I'm not quite as skilled at rigging as I would like to be, but I can usually solve simple problems. I've been working at this IK Arm for days now and can't seem to figure out what's going wrong.

Here's the situation. I'm rigging a little boy character whose arms are modeled straight out. I then try to add an IK Handle (RP) from the shoulder to the wrist joint. I know that in order to move it, I will group the IK Handle to itself, and set the pivot to the base of the hand. Conceptually, I think I'm on the right track. BUT!!! When I add the handle, the elbow bends slightly out of the bind position and when I test the motion by moving the handle, the elbow bends all over the place, rotating the hand and everything out of position. I've tried playing with the preferred angle of the elbow, but once again, to no avail. My limited knowledge in rigging has left me dry and I may be forced to use simple controller for an FK arm, which in the long run would hurt the animation. Let me know if I can further explain.

-green

GreenShellFactor

04-09-2007, 03:10 AM

I forgot to mention that I've already set up set driven keys for the movement of the hand and that the bones of the hand have been moved and reoriented...if that helps at all. Thanks again.

~green

P.S. I'm also not too sure as to WHEN I should be orienting/freezing joint transformations.

peepshow

04-19-2007, 01:44 PM

hmm, its hard to visualise without seeing it but when you created the initial bone set-up, did you create a slight bend at the elbow to begin with? you mention your charcters arms are straight out, but if you create the bones in the top viewport and create a slight angle between the upper and lower arm, towards the direction you want the arms to bend that generally helps! it does sound like a preferred angle thing!!

ErikSvensson

04-19-2007, 06:28 PM

Create the arm in the top view, with a little bend, not to much, but slightly, so the IK know were to point. / \ like that, but more subtle. Then when you feel like the positions for the arms are correct, test bind the mesh, move around and adjust the joints placements. Then you freeze and fix the orientation of the joints. Then setup controllers etc etc.

Good luck! :)

Erik

GreenShellFactor

04-23-2007, 01:01 AM

Thanks for the reply, all. I ended up just sticking with an FK setup for the arms since I don't really need IK for this character. But ya'll were right about the IK arm being perfectly straight. Knowledge acquired :) Thanks again!

~green

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